1. Field of the Invention
This invention relates to a solid state image pickup device with deposited photoelectric conversion layers, which will be hereinafter also called color sensor, and in particular to an image pickup device close to the spectral sensitivity of human eyes and moreover with no pseudocolor.
2. Description of the Related Art
A solid state image pickup device in a related art has a structure wherein a photoelectric conversion layer is provided on almost the same plane as a charge transfer passage. However, this structure has disadvantages in that if the pixel size approaches the same degree as the light wavelength with an increase in the number of pixels, it becomes hard to guide light to the photoelectric conversion layer and that degradation of light use efficiency caused by the light loss in a color filter cannot be avoided. Further, since R color light, G color light, and B color light are detected at different positions, color separation may occur, causing pseudocolor to occur. Thus, to avoid this, a low-pass filter is required and thus light loss is also caused by the filter. If emerald color is added to a color filter to provide four colors, the problem of pseudocolor is not solved.
As a solution to such a weak point of the solid state image pickup device of the photoelectric conversion layer of planar placement type in the related art, a solid state image pickup device with a light reception section as a deposition structure was already proposed in JP-A-58-103165 in 1983. Color sensors each wherein as specific deposition means, a deposited light reception section is formed using the wavelength dependency of the absorption coefficient of an Si semiconductor and color separation is performed in the depth direction are reported in JP-A-7-38165, U.S. Pat. No. 5,965,875 and U.S. Pat. No. 6,632,701. However, the disclosed arts involve problems of broad wavelength dependency of the spectral sensitivity in the deposited light reception section and insufficient color separation. Particularly, color separation of blue and green is insufficient.
To solve the problems, US2003/0209651A1 proposes a method of providing a sensor unit for accepting green light on the top of a light reception element of an Si semiconductor and receiving blue color light and red color light at the light reception element of an Si semiconductor. However, the method also has the disadvantage in that the difference from the spectral sensitivity of the visual sense of a human being is large.
In Japanese Patent No. 2872759, an attempt is made to take in light in the intermediate range of blue light and green light in a single-plate system and a multiplate system and is added to computation processing of received light image information, thereby providing image information matched with the spectral sensitivity of the visual sense of a human being. However, correction of the spectral sensitivity is also insufficient in the single-plate system and the multiplate system. Further, Japanese Patent No. 3315213 reports a deposition sensor wherein the charge move speed of an organic semiconductor is adjusted and the electric signal of an image is made finer, but the spectral sensitivity close to the sensibility of a human being cannot yet be realized.
As described above, if the image pickup part of the color sensor is put into multiple layers to improve the sensitivity, pseudocolor, etc., the color reproducibility of a played-back (reproduced) image becomes insufficient because of the alienation from the spectral luminous efficacy, and means for satisfying both the sensitivity and the color quality cannot yet be provided.